Inhalation exposure to the more volatile PCBs in urban areas, near the Great Lakes, in areas where dredging is occurring, and at landfills and remediation sites has the potential to cause neurological, reproductive, and immunological toxicity in animals and humans. Projects 1, 2, and 3 will investigate the toxicological responses to atmospheric PCBs. We propose an Inhalation Toxicology Core within the isbrp to support these Projects. Our primary goal is to serve the other research support cores and the projects with state-of-the-art animal facilities and rigorously controlled inhalation exposures to realistic mixtures of airborne PCB congeners. In order to achieve this goal, we have established four specific aims: Aim 1) Generate controlled PCB atmospheres in exposure chambers and collect airborne PCBs resulting from vaporization of common industrial PCB mixtures to facilitate the creation of a model exposure mixture, (supports Projects 1, 2, 3, 5 and the Synthesis Core) Aim 2) Perform acute, subacute and subchronic inhalation exposures to laboratory animals to defined mixtures of atmospheric PCBs and to individual congeners, (supports Projects 1, 2, and 3) Aim 3) Provide a rodent vivarium for experimental animals used for the isbrp and execute a quality assurance program to monitor their health and welfare, (supports Projects 1, 2, and 3) Aim 4) Perform necropies on exposed, control and sentinel rodents and distribute tissues to project investigators in the isbrp. (supports Projects 1, 2, and 3) The Inhalation Toxicology Core will be created within the existing Inhalation Toxicology Facility (ITF) of the Environmental Health Sciences Research Center which consists of 6,000 ft2 of contiguous laboratories and offices. The ITF is nationally recognized for innovative animal models and exposure delivery systems. A full array of inhalation toxicology, aerosol science, and bioassay services are rendered. The Inhalation Toxicology Core is well equipped for generating and quantifying PCB vapors or aerosols;for performing nose-only inhalation exposures of rats in acute, subacute or subchronic protocols;and for determining the degree of exposure and response. The development of innovative exposure delivery systems for PCB mixtures representative of atmospheric congeners is an essential concurrent activity.